The present invention relates to generally a traverse motion used in combination with a device for winding a continuous elongate element around a spool and more particularly a traverse motion adapted to produce packages of large-diameter strands consisting of a large number of glass filaments.
In general, conventional bushings used for producing glass fibers have been provided with orifices from 400 to 800 in number and glass filaments drawn through such bushings have been from 10 to 13 microns in diameter. In order to form packages of roving with a desired diameter from such glass filaments, there has been required such a cumbersome process that glass filaments from 400 to 800 in number drawn from each bushing are gathered into a strand which in turn is wound around a spool to form a cake and thereafter strands are unwound from 15 to 30 cakes and gathered into a roving which in turn is wound around another spool to form a package.
However, recently there have been devised and demonstrated various multiple-nozzle spinning techniques of the type in which glass filaments from 2000 to 4000 in number and from 15 to more than 20 microns in diameter can be simultaneously spun from a single bushing so that packages can be directly formed by merely gathering these glass filaments into a strand which in turn is wound around a spool to form a package. Since packages can be formed by one step, productivity has been considerably improved, but with the conventional winding devices, it is impossible to produce packages with high qualities. Packages with high qualities mean (1) that every package is almost in the form of a correct cylinder which has the parallel bases or ends perpendicular to the axis of the package and whose peripheral surface is completely free from ridges and valleys; that is, every package has square ends; (2) that the whole length of strand of every package is uniform in diameter and is free from fuzz; and (3) that every package has a uniform hardness from the center to the peripheral surface.
It follows therefore that in order to obtain such packages with high qualities, one of the conditions which must be satisfied is that the strand winding tension must be maintained always constant so that the strand wound has a uniform diameter and the formed packages have a uniform hardness as described above. This condition is also important in order to stabilize the spinning operation of multiple-nozzle bushings which are very sensitively influenced by the variations in glass filament drawing tension. More over, since the strand applied with a lubricant is very slippery, the variations in winding tension tend to cause such strand to slip off from the ends of the package being formed so that the resultant package may get out of the shape having square ends. In addition, the strand wound into the package is flattened at various portions so that fuzz is produced. Thus the qualities of the packages are degraded. Furthermore when the strand is unwound, it bonds itself so that the smooth unwinding cannot be effected. In order to maintain a uniform winding tension, the strand winding speed must be maintained uniform. To this end, there have been employed a method in which the rotational speed of a spool is decreased in inverse proportion to the quadratic increase in diameter of the package being formed so that the peripheral or surface speed of the package can be maintained uniform.
In order to obtain high-quality packages with square ends, another problem must be taken into consideration. The problem is the delay in response of strand which is inevitable to transverse motions. More specifically, when the strand is wound around a spool, it is traversed by a traverse motion. In this case, the traversing movement of strand lags behind the reciprocating movement of a strand guide by some time. As a result, the traversing movement of strand is suspended or dwells for some time interval at each returning point so that the diameter at each end of a package becomes greater than that of the intermediate portion and consequently the finished package becomes in the form like a hand-drum. In general, the higher the traversing speed, the longer the relative delay in response of strand becomes. This dwelling problem becomes therefore very serious especially in the case of the production of packages for F.R.P. because these packages must have a large traverse angle (the angle between a wound strand and a plane perpendicular to the axis of the spool) and consequently a high traversing speed is needed. In order to overcome this problem, there has been devised and demonstrated a method in which a pressure roller is constantly pressed against the surface of a package being formed, thereby making the surface flat. However, obviously the more pronounced the hand-drum form becomes, the higher the pressing force becomes. As a result, turns of strand at the ends of a package being formed slip off, thus causing the ends of the package to collapse. In addition, since the pressure roller exerts higher pressure against the ends of a package being formed, turns of strand at the ends become flat. Especially in the case of the production of packages for F.R.P. which must satisfy a strict requirement on a uniform quality of strand, flattening of strand must be avoided. Furthermore, the increase in contact pressure of the pressure roller against a package being formed results in vibrations of the traverse motion so that the strand comes off from the strand guide and other malfunctions tend to occur.
In order to solve the problem of the package formed into the hand-drum form only by means of the traverse motion, there has been devised and demonstrated a method in which a scroll cam is provided with a 1/4 (2n+1) wind cam groove, where n is any natural number, so that the strand guide returns its initial position after two reciprocating motions and two returning points of the cam groove at each end of the scroll cam are staggered so that there are two different returning points of the strand at each end of a package being formed. This method serves to suppress the formation of the enlarged-diameter ends of the package to some extent, but cannot eliminate them completely.